// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.

#ifndef STORAGE_LEVELDB_UTIL_MUTEXLOCK_H_
#define STORAGE_LEVELDB_UTIL_MUTEXLOCK_H_

#include "port/port.h"
#include "port/thread_annotations.h"

namespace leveldb {

// Helper class that locks a mutex on construction and unlocks the mutex when
// the destructor of the MutexLock object is invoked.
//
// Typical usage:
//
//   void MyClass::MyMethod() {
//     MutexLock l(&mu_);       // mu_ is an instance variable
//     ... some complex code, possibly with multiple return paths ...
//   }

    class SCOPED_LOCKABLE MutexLock {
    public:
        explicit MutexLock(port::Mutex *mu) EXCLUSIVE_LOCK_FUNCTION(mu)
                : mu_(mu) {
            this->mu_->Lock();
        }

        ~MutexLock() UNLOCK_FUNCTION() { this->mu_->Unlock(); }

        MutexLock(const MutexLock &) = delete;

        MutexLock &operator=(const MutexLock &) = delete;

    private:
        port::Mutex *const mu_;     //不能指向其他Mutex变量，但是mu_值可以修改
    };

}  // namespace leveldb


#endif  // STORAGE_LEVELDB_UTIL_MUTEXLOCK_H_
